Brake piston support

Hello together, 3 days ago my brake (front left) started to get hot and (obviously) no longer glide back decently. Saddle and rim were very hot. I now took down the saddle at Easter-WE and found out that the cuff had torn and thus water had penetrated. The piston looks accordingly “eating”: however, the system slowed down until the end “normal”. Here my questions: 1. I do not get the piston pushed out of the saddle. (drawn) – what can this be? Is the piston in any form secured against “discharge”? 2. Can a “eating” piston be re-reprocessed (easy lubricating so that it can be re-installed in the saddle. (with new cuff)? 3. Work in my case if necessary repair kits – does anyone have experience with it? Greetings and thanks – and… there is something Ralf rushing.